Tube and bourdon spring



Sept. 19, 1950 c. H. DICKSON TUBE AND BOURBON SPRING Filed July 15, 1947INVENTOR. CHARLES H. DICKSON ATT NEY Patented Sept. 19, 1950 TUBE ANDBOURBON SPRING Charles H. Dickson, Rochester, N. Y., assignor to TaylorInstrument Companies, Rochester, N. Y., a corporation of New YorkApplication July 15, 1947, Serial No. 761,076

3 Claims.

This invention relates to an improved tubing as well as to a Bourdonspring made therefrom.

The Bourdon spring which has long been used in measuring instruments iscurrently made from drawn metal tubing of circular cross section. Anyscratch or defect present in the billet from which the tube is drawnfrequently is present as a line of weakness in the finished tube.Usually this line of weakness is so minute that it is not observed untilthe failure of a Bourdon spring made from such a weakened tube.

An important feature of the present invention relates to a Bourdonspring in which minor weaknesses of the type mentioned are sodistributed that they rarely cause failures.

Other features and advantages of the invention will appear from thedetailed description and claims in which:

Fig. 1 is a perspective view of a metal tube having longitudinal linesof weakness therein;

Fig. 2 is a perspective view of such tubing that has been flattened, inreadiness to be coiled into a Bourdon spring;

Fig. 3 is a perspective view of an improved tube of the presentinvention showing how any longi tudinal lines of weakness in the tubewill be spirally arranged around its axis; and

Fig. 4 is a perspective View of the improved tube of Fig. 3 after it hasbeen flattened in readiness to be coiled into a Bourdon spring.

Fig. 5 discloses a Bourdon spring made from this improved tubing.

Tubing 5 and especially metal tubing that has been formed from a billetby successive draws in accordance with conventional metal working hassurface defects in the form of seams or scratch marks extendinglengthwise of the tube. These defects are indicated by the dotted lines6 in Fig. 1 since frequently they are not visible to the naked eye untilthe tube is deformed by flattening, as shown in Fig. 2. These defectsthen become easily visible as parallel fissures or scratch marks 6aextending along the tube. Each fissure or scratch mark constitutes aline of weakness which, if it occurs at or near the edge of theflattened tube, will frequently initiate failure of the finished Bourdonspring.

In accordance with the present invention, a strengthened tube 7 isillustrated in Fig. 3. This strengthening is obtained by twisting thetubing around its longitudinal axis; such as by twisting between drawingpasses, or simultaneously with drawing, or after drawing to the desiredsize.

Preferably, the twisting is eifected uniformly throughout the length ofthe tube. This is conveniently effected by gripping the tube at its endsand then twisting the tube until the lines of weakness which werepreviously linear, are uniformly and spirally arranged on the surfacesof the tube, as indicated at la.

The tube thus twisted can then be flattened in the usual manner and thenwound into the well known Bourdon coil 9 (Fig. 5) of the helical or flattype, the flat type only being illustrated. It will be noted that thelines of weakness la extend across each convolution of the spring. Inthis way no line of weakness extends along the edges of the spring wherefailures usually develop.

What I claim is:

1. A Bourdon spring or the like comprising a curved, flattened tube, thematerial of which has been displaced spirally around the flattened tubethroughout substantially the entire length thereof without substantiallychanging the physical shape of the tube.

2. A Bourdon spring or the like comprising a coiled, flattened tube, thematerial of which has been twisted throughout substantially its entirelength around the passage through the tube without substantiallychanging the physical shape of the tube whereby any weakness extendinglengthwise of the original tube from which the spring is made, isdistributed across the convolutiions of the coil of the finished spring.

3. A pressure responsive element comprising a partially collapsed tube,the material of which has been displaced spirally around the passagethrough the tube substantially throughout its entire length withoutsubstantially changing the physical shape of the tube.

CHARLES H. DICKSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,826,077 Johnson dot. 6, 19312,346,376 Heavener Apr. 11, 1944 FOREIGN PATENT$ Number Country Date12,889 Great Britain June 15, 1850 477,992 Great Britain Jan. 10, 1938

